Structure and binding in molecular complexes of cyclic polyethers. III. Host–guest interaction involving two assemblies of binding sites

Abstract

The crystal structure of the one-to-one complex between a synthetic ligand (I) (C40Hs00~z) containing two 18-crown-6 macrocyclic moieties and a bis(hexafluorophosphate) salt of tetramethylenediamine has been determined by X-ray diffraction methods at low temperature (-160°C). Crystals are orthorhombic, space group Pben, with a = 18-971 (3), b = 19.137 (3), c = 13.932 (2)/l,, and Z = 4. The structure was solved by direct methods and refined by full-matrix least-squares methods to R =0.059 for 2371 independent reflexions measured by counter diffractometry. In the solid, the molecules are located on crystallographic twofold axes. The macro-ring assemblies of binding sites in the host are held in a convergent relationship through hydrogen bonding to functional groups of the guest species. The ammonium ions centre into the inside faces of the macrocycles, the tetramethylene chain being strung between the two rings. All the N to O distances range from 2.9 to 3.1 ,~,, suggesting that direct N ÷... :(3 interactions are involved in stabilizing the host-guest complex. Molecular conformation and dimensions, and the geometry of the intermolecular binding are described in detail.

The Voyage of Goldberg: Supramolecular Chemistry and Memories

“…Following the completion of his doctoral degree, Prof. Goldberg decided to pursue a postdoctoral position at UCLA. After his stay at UCLA, Prof. Goldberg rejoined Tel Aviv University as a faculty member, where he continued to study the crystallographic features of various polycyclic ethers and their host–guest interactions. − Prof. Goldberg’s research as a university professor involved collaborations with notable scientists such as Donald J. Cram at UCLA, who shared the 1987 Nobel Prize in Chemistry together with Jean-Marie Lehn and Charles J. Pedersen. While giving his Nobel lecture and referencing his award-winning research, Cram stated: “By the end of 1986, Drs.…”

A non-symmetric water complex of a tripod ligand: the structure of tris[(2-methyl-8-quinolyloxy)ethyl]amine dihydrate

“…Bond lengths and angles are given in Tables 2 and 3. Diseussion. Organic polar molecules or ions such as malononitrile, tetramethylenediammonium or thiourea can replace metal cations in host-guest complexes of cyclic crown ethers (Kaufmann, Knoechel, Kopf, Oehler & Rudolph, 1977;Goldberg, 1977) and also of linear oligoethers (Weber & Saenger, 1980b). Normally, water is only involved in linking ligands, as in the dimeric structure of a complex (Weber & Saenger, 1980a).…”

The 1:1 complex of KSCN with a macrocyclic polyether ligand system containing two phosphonate groups at the binding site

“…The naphthyl group was refined as a rigid group with internal coordinates found in the complex of another binaphthyl crown that has two equivalent crown rings, which interact with the [H3N(CHE)4NH3] 2+ ion (Goldberg, 1977). One of the ethyl groups is disordered, with refined occupancies for C (24) (24)] were not included in the structure-factor calculations.…”